This invention relates generally to sealing assemblies, and more particularly to a remotely actuated stab-in sealing assembly for effecting a metal-to-metal seal between a tubular member, such as a pack-off nipple of an underwater oil or gas well, and the wall of a bore within which the tubular member is received, such as a tubing hanger bore.
Various means have heretofore been used to seal around tubular elements in a wellhead. Elastomeric rings have been used, an example being the O-rings and packing elements of elastomeric material shown in U.S. Pat. No. 2,830,665 to Burns et al. Unfortunately, elastomeric seals, such as those disclosed in Burns, have experienced difficulties in containing, by themselves, the high bottom hole pressures encountered during service. Elastomeric seals also can break down when exposed to chemicals, heat, or other adverse elements in the sometimes-harsh subsea oil and gas well environment.
Another example of a wellhead seal is disclosed in U.S. Pat. No. 2,992,840 to Reynolds et al., which is directed to a frustoconical-shaped metal gasket which is compressed between two flanges having a greater cone angle so that the gasket is deformed, the edges of the gasket being "coined" so as to closely engage elements of the flanges and provide a metal-to-metal seal. Although these and other prior art metal ring gaskets can withstand the high pressures and harsh environments encountered in underwater oil or gas well service, some problems have been experienced which result in their being unsuitable for some applications. Sometimes the metal ring gaskets have a tendency to gall the tubing hanger bore or other bore into which the gaskets are stabbed, making it difficult to obtain a light seal on the damaged surfaces and possibly incapacitating the equipment for future use without costly or time-consuming repairs. Sometimes the metal ring gaskets of the prior art cannot accommodate the uncertainty, due to the manner in which the underwater well components are assembled down hole, as to the respective axial positions of the two surfaces which are to be sealed against This low "stack-up tolerance" of some prior art metal seal rings can result in an improperly energized seal. Moreover, even when properly initially energized, sometimes problems arise with prior art metal seal rings when the sealed surfaces experience slight axial movements with respect to each other during service. Loss of sealing function or improper energization can sometimes result.
It is the object of the present invention to overcome these and other deficiencies and problems experienced with prior art metal seal rings.